The problem is that it gets bogged down really bad, and sputters it acts like its not getting the right amount of fuel or sporadic spark. Here is what happened.

Last night when she started acting up it was after I had driven her about thirty miles. The tires need balancing really bad so the car has a killer shudder at 65 on up so I was trying to keep my highway speed under that.
It did not do it on the way up and it sat in the yard for about 2 1/2 hours while I worked, I had to start it once and move it about 30 feet to get out of someones way and shut it back down. The problem started about 3 miles after I left the boneyard and was limited but got progressively worse as I drove. I pulled into town and stopped under a street lamp and she was fine at idle, revved her up to 2500 (highway avg) with no problems at all. Decided to try and make it to the next stopping point several miles away, same thing almost as soon as I got her on the highway she started acting up again and got progressively worse, I pulled into Wright city and again checked under a street lamp same thing ran fine. Pulled her back onto the highway and went two miles and it started again, stopped in foristell under street light same thing, ran fine pulled back onto the highway and started again, pulled through wentzville and kept on going, by the time I reached the 40 exit it was so bad I pulled over onto the shoulder and coasted to a stop in neutral, still acting up, I looked (no light) but could not find anything in particular so I turned it off and waited about 10 minutes. Started up again and still same problem, limped down the shoulder until I got to an entrance ramp and she suddenly got some wind and picked up enough to pull back onto the highway but still running bad, did a couple more shoulder limps into lake st louis and I got down into some slow speeds and she was generally fine but still indicated poor behavior. Got it home and frustrated I left it alone.

After awhile I decided to turn it on again and no problems, I rolled around town close to home to see if I could make it happen again, nothing, it was cooled down plenty before I started driving again. Romped her in a couple of empty parking lots but I could not get it up to highway speeds as I did not want to get stranded on the highway. Then on the way back home she sputtered once pretty bad but not anymore I drove up and down fiese several times trying to make it happen again but to no avail.

Today, I had a breakfast meeting, and had to work so I just got home and tried the codeing thing but no code showed up at all. I started it and drover it around for a few minutes and nothing, it runs fine around town.

So here is what I have noticed that might have an impact on trouble shooting: only happens when warmed up, only happens at 55 mph and up, gets progressively worse as the problem continues. Update: Now it does it full time. Whatever the part was it is now completely gone. It does it when I put it in drive but not in park or neutral, not quite as bad in reverse. It gets to stumbling so bad it has stalled a few times.

89 firebird GTA, 5.7 tpi, bought used and as far as I can tell the engine has not been modified in any way yet.

Anyone ever experience this before?
Any help would be most appreciated

 

I'd start by looking over the ignition system closely. Take a good look at the cap and rotor, then inspect the reluctor and pickup coil, and meter the pickup coil windings.

I'm thinking ignition because fuel delivery problems usually don't go away and then resurface, they generally just happen and stay that way.

 

Thanks Vader, I sort of felt the same way, though I did replace the fuel filter and it DID need to be replaced, this did not cure the problem so I started checking out the ignition really good, I was looking at the wires for bad spots etc, but they are fairly clean inside at the metal connectors and the color of the wires themselves are fairly bright and look pretty new in general (I was going to replace them anyway but when you are short on cash and something already looks new why spend the money on it when there are other priorities, ya know) The dist cap also looks new, viewing the inside of the cap there is very little dust collected and from what I have seen an older cap will be pretty dirty inside, rotor is in the same condition. The timing does need to be adjusted I can hear it resonating while running, but its not too bad, and I somehow cannot realte that to running great in park/neutral then turning to crap the second I put her in Odrive or drive. The consistency of problem on in drive and off when not is starting to lead me towards a switch or sensor on the tranny that indicates the car is now ready to do something other than look pretty and sound good. Could that still be an ignition problem? Tranny fluid level is optimal (and clean, doesn't taste very good but its still clean) Do you know of any such switch/sensor? Haynes is pretty pathetic and I cannot find a Chiltons or afford a Helms yet.